1. Field of Invention
The present invention is related to a wireless local area network (WLAN) or other suitable network; and more particularly, to a new and unique method and apparatus for providing an estimate of a mobile location of a wireless node, point or terminal in an 802.11 WLAN.
2. Description of Related Art
FIG. 1 shows, by way of example, typical parts of an IEEE 802.11 WLAN system, which is known in the art and provides for communications between communications equipment such as mobile and secondary devices including personal digital assistants (PDAs), laptops and printers, etc. The WLAN system may be connected to a wire LAN system that allows wireless devices to access information and files on a file server or other suitable device or connecting to the Internet. The devices can communicate directly with each other in the absence of a base station in a so-called “ad-hoc” network, or they can communicate through a base station, called an access point (AP) in IEEE 802.11 terminology, with distributed services through the AP using local distributed services (DS) or wide area extended services, as shown. In a WLAN system, end user access devices are known as stations (STAs), which are transceivers (transmitters/receivers) that convert radio signals into digital signals that can be routed to and from communications device and connect the communications equipment to access points (APs) that receive and distribute data packets to other devices and/or networks. The STAs may take various forms ranging from wireless network interface card (NIC) adapters coupled to devices to integrated radio modules that are part of the devices, as well as an external adapter (USB), a PCMCIA card or a USB Dongle (self contained), which are all known in the art.
FIGS. 2a and 2b show diagrams of the Universal Mobile Telecommunications System (UMTS) packet network architecture, which is also known in the art. In FIG. 2a, the UMTS packet network architecture includes the major architectural elements of user equipment (UE), UMTS Terrestrial Radio Access Network (UTRAN), and core network (CN). The UE is interfaced to the UTRAN over a radio (Uu) interface, while the UTRAN interfaces to the core network (CN) over a (wired) Iu interface. FIG. 2b shows some further details of the architecture, particularly the UTRAN, which includes multiple Radio Network Subsystems (RNSs), each of which contains at least one Radio Network Controller (RNC). In operation, each RNC may be connected to multiple Node Bs which are the UMTS counterparts to GSM base stations. Each Node B may be in radio contact with multiple UEs via the radio interface (Uu) shown in FIG. 2a. A given UE may be in radio contact with multiple Node Bs even if one or more of the Node Bs are connected to different RNCs. For instance, a UE1 in FIG. 2b may be in radio contact with Node B2 of RNS1 and Node B3 of RNS2 where Node B2 and Node B3 are neighboring Node Bs. The RNCs of different RNSs may be connected by an Iur interface which allows mobile UEs to stay in contact with both RNCs while traversing from a cell belonging to a Node B of one RNC to a cell belonging to a Node B of another RNC. The convergence of the IEEE 802.11 WLAN system in FIG. 1 and the (UMTS) packet network architecture in FIGS. 2a and 2b has resulted in STAs taking the form of UEs, such as mobile phones or mobile terminals. The interworking of the WLAN (IEEE 802.11) shown in FIG. 1 with such other technologies (e.g. 3GPP, 3GPP2 or 802.16) such as that shown in FIGS. 2a and 2b is being defined at present in protocol specifications for 3GPP and 3GPP2.
The IEEE 802.11 WLAN system in FIG. 1 and the (UMTS) packet network architecture in FIGS. 2a and 2b, and the convergence thereof, must meet certain requirements, including those set forth by the Federal Communications Commission (FCC). In particular, the FCC has recently defined a set of accuracy requirements for E-911 calls, which are collectively known in the industry as the E-911 Phase II mandate. The mandate states that handset-based solutions should locate the E-911 caller to within 50 meters for 67% of the calls and to within 150 meters for 95% of the calls. The new ALI (Automatic Location Identification)-capable handsets must fulfill the FCC's E-911 Phase II location accuracy requirement.
Several location systems have been designed for wide-area cellular systems in the art. Two of the most prevalent technologies are the AFLT (Advanced Forward-Link Trilateration) and AGPS (Assisted GPS) methods. While these systems have been found to be promising for outdoor environments, their effectiveness in indoor environments is limited by the severe indoor multipath effect and in-building penetration loss, which, in particular, limits the reception of GPS transmissions. There are also some indoor location systems that rely on specialized hardware solutions, such as IR (infrared) and RFID-based technologies. However, these indoor location systems typically suffer from limited range and they also require extensive deployment of an infrastructure whose sole purpose is to locate people.
The present invention provides a new and effective approach for meeting the requirements of the E-911 Phase II mandate as well as the voice/data communications.